Cis-1,4-polydienes with improved cold flow resistance

ABSTRACT

A method for preparing cis-1,4-polydienes having useful resistance to cold flow, the method comprising the steps of preparing a polymerization system including a reactive polymer by introducing a lanthanide-based catalyst and a conjugated diene monomer and adding a Lewis acid to the polymerization system including a reactive polymer.

This application is a U.S. National Stage Application under 35 U.S.C. §371 of International Application No. PCT/US2016/015411 filed on Jan. 28,2016, and claims benefit of U.S. Provisional Application Ser. No.62/108,883, filed Jan. 28, 2015, U.S. Provisional Application Ser. No.62/108,839, filed Jan. 28, 2015, and U.S. Provisional Application Ser.No. 62/108,899, filed Jan. 28, 2015, which are incorporated herein byreference.

FIELD OF THE INVENTION

Embodiments of the present invention are directed towardcis-1,4-polydienes having improved cold flow characteristics. Thepolydienes are prepared using a lanthanide-based catalyst and treatedwith a Lewis acid.

BACKGROUND OF THE INVENTION

Lanthanide-based catalyst systems are known to be useful forpolymerizing conjugated diene monomers to form polydienes having highcis-1,4-linkage contents, low 1,2-linkages, and linear backbones. Thesecis-1,4-polydienes containing a linear backbone are believed to providebetter tensile properties, higher abrasion resistance, lower hysteresis,and better fatigue resistance as compared to the cis-1,4-polydienesprepared with other catalyst systems such as titanium-, cobalt-, andnickel-based catalyst systems. Therefore, the cis-1,4-polydienes madewith lanthanide-based catalysts are particularly suitable for use intire components such as sidewalls and treads.

However, one disadvantage of the cis-1,4-polydienes prepared withlanthanide-based catalysts is that the polymers exhibit high cold flowdue to their linear backbone structure. The high cold flow causesproblems during storage and transport of the polymers and also hindersthe use of automatic feeding equipment in rubber compound mixingfacilities.

Cis-1,4-polydienes synthesized with lanthanide-based catalyst systemsmay also display pseudo-living characteristics in that, upon completionof the polymerization, some of the polymer chains possess reactive endsthat can react with certain functionalizing agents to yieldfunctionalized cis-1,4-polydienes. These functionalizing agents havebeen employed to improve the cold flow resistance of the resultingpolydienes. Nevertheless, whether a particular functional group impartedto a polymer can improve the cold flow resistance or reduce hysteresisis often unpredictable. Furthermore, functionalizing agents that workfor one type of polymer do not necessarily work for another type ofpolymer, and vice versa.

Therefore, there is a need to develop a process for producingfunctionalized cis-1,4-polydienes having a combination of high ciscontent and a linear backbone as well as improved cold flow resistance.This combination of properties in a polymer will provide a tire withsuperior performance.

SUMMARY OF THE INVENTION

One or more embodiments of the present invention provide a method forpreparing cis-1,4-polydienes having useful resistance to cold flow, themethod comprising the steps of preparing a polymerization systemincluding a reactive polymer by introducing a lanthanide-based catalystand a conjugated diene monomer; and adding a Lewis acid to thepolymerization system including a reactive polymer.

Other embodiments of the present invention provide a vulcanizablecomposition comprising a filler, a curative and a cis-1,4-polydienesprepared by a method comprising the steps of polymerizing conjugateddiene monomer with a lanthanide-based catalyst to form a reactivepolymer; and treating the reactive polymer with a Lewis acid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the cold-flow resistances of thecis-1,4-polybutadiene samples synthesized in Examples 1-2, plottedagainst the polymer Mooney viscosity.

FIG. 2 is a graph of the cold-flow resistances of thecis-1,4-polybutadiene samples synthesized in Examples 3-4, plottedagainst the polymer Mooney viscosity.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments of the invention are based, at least in part, on thediscovery of a method for producing cis-1,4-polydienes havingtechnologically useful resistance to cold flow. According to aspects ofthe invention, cis-1,4-polydienes having reactive chain ends areprepared from conjugated diene monomer and then treated with a Lewisacid prior to quenching the polymerization. Without wishing to be boundby any particular theory, it is believed that by treating thecis-1,4-polydienes prior to quenching the polymerization, the polymerchains are at least partially coupled or otherwise networked, whichprovides the desired cold flow resistance. Moreover, it has beenobserved that while the cold flow resistance of the polymer is improved,the Mooney viscosity of the polymer is not deleteriously altered,especially at high shear. Additionally, vulcanizates prepared usingcis-1,4-polydienes of one or more embodiments show improved propertiessuch as reduced hysteretic loss.

Monomer

Examples of conjugated diene monomer include 1,3-butadiene, isoprene,1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl 1,3-butadiene,2-ethyl-1,3-butadiene, 2-methyl-1,3-pentadiene, 3-methyl-1,3-pentadiene,4-methyl-1,3-pentadiene, and 2,4-hexadiene. Mixtures of two or moreconjugated dienes may also be utilized in copolymerization.

Catalyst System

In one or more embodiments, the catalyst system employed in the presentinvention is a coordination catalyst system. In particular embodiments,the coordination catalyst system is a lanthanide-based catalyst system.In one or more embodiments, the catalyst system is a preformedlanthanide-based catalyst system. In other embodiments, the catalystsystem is a lanthanide-based catalyst system form in situ.

Coordination Catalyst System

Coordination catalyst systems are generally known. The key mechanisticfeatures of coordination polymerization have been discussed in books(e.g., Kuran, W., Principles of Coordination Polymerization; John Wiley& Sons: New York, 2001) and review articles (e.g., Mulhaupt, R.,Macromolecular Chemistry and Physics 2003, volume 204, pages 289-327).Coordination catalysts are believed to initiate the polymerization ofmonomer by a mechanism that involves the coordination or complexation ofmonomer to an active metal center prior to the insertion of monomer intoa growing polymer chain. An advantageous feature of coordinationcatalysts is their ability to provide stereochemical control ofpolymerizations and thereby produce stereoregular polymers. As is knownin the art, there are numerous methods for creating coordinationcatalysts, but all methods eventually generate an active intermediatethat is capable of coordinating with monomer and inserting monomer intoa covalent bond between an active metal center and a growing polymerchain. The coordination polymerization of conjugated dienes is believedto proceed via π-allyl complexes as intermediates. Coordinationcatalysts can be one-, two-, three- or multi-component systems. In oneor more embodiments, a coordination catalyst may be formed by combininga heavy metal compound (e.g., a transition metal compound or alanthanide-containing compound), an alkylating agent (e.g., anorganoaluminum compound), and optionally other co-catalyst components(e.g., a Lewis acid or a Lewis base). In one or more embodiments, theheavy metal compound may be referred to as a coordinating metalcompound.

Lanthanide-Based Catalyst System

Practice of the present invention is not necessarily limited by theselection of any particular lanthanide-based catalyst system. In one ormore embodiments, the catalyst systems employed include (a) alanthanide-containing compound, (b) an alkylating agent, and (c) ahalogen source. In other embodiments, a compound containing anon-coordinating anion or a non-coordinating anion precursor can beemployed in lieu of a halogen source. In these or other embodiments,other organometallic compounds, Lewis bases, and/or catalyst modifierscan be employed in addition to the ingredients or components set forthabove. For example, in one embodiment, a nickel-containing compound canbe employed as a molecular weight regulator as disclosed in U.S. Pat.No. 6,699,813, which is incorporated herein by reference.

Lanthanide-Containing Compounds

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include a lanthanide-containing compound.Lanthanide-containing compounds useful in the present invention arethose compounds that include at least one atom of lanthanum, neodymium,cerium, praseodymium, promethium, samarium, europium, gadolinium,terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, anddidymium. In one embodiment, these compounds can include neodymium,lanthanum, samarium, or didymium. As used herein, the term “didymium”shall denote a commercial mixture of rare-earth elements obtained frommonazite sand. In addition, the lanthanide-containing compounds usefulin the present invention can be in the form of elemental lanthanide.

The lanthanide atom in the lanthanide-containing compounds can be invarious oxidation states including, but not limited to, the 0, +2, +3,and +4 oxidation states. In one embodiment, a trivalentlanthanide-containing compound, where the lanthanide atom is in the +3oxidation state, can be employed. Suitable lanthanide-containingcompounds include, but are not limited to, lanthanide carboxylates,lanthanide organophosphates, lanthanide organophosphonates, lanthanideorganophosphinates, lanthanide carbamates, lanthanide dithiocarbamates,lanthanide xanthates, lanthanide β-diketonates, lanthanide alkoxides oraryloxides, lanthanide halides, lanthanide pseudo-halides, lanthanideoxyhalides, and organolanthanide compounds.

In one or more embodiments, the lanthanide-containing compounds can besoluble in hydrocarbon solvents such as aromatic hydrocarbons, aliphatichydrocarbons, or cycloaliphatic hydrocarbons. Hydrocarbon-insolublelanthanide-containing compounds, however, may also be useful in thepresent invention, as they can be suspended in the polymerization mediumto form the catalytically active species.

For ease of illustration, further discussion of usefullanthanide-containing compounds will focus on neodymium compounds,although those skilled in the art will be able to select similarcompounds that are based upon other lanthanide metals.

Suitable neodymium carboxylates include, but are not limited to,neodymium formate, neodymium acetate, neodymium acrylate, neodymiummethacrylate, neodymium valerate, neodymium gluconate, neodymiumcitrate, neodymium fumarate, neodymium lactate, neodymium maleate,neodymium oxalate, neodymium 2-ethylhexanoate, neodymium neodecanoate(a.k.a., neodymium versatate), neodymium naphthenate, neodymiumstearate, neodymium oleate, neodymium benzoate, and neodymiumpicolinate.

Suitable neodymium organophosphates include, but are not limited to,neodymium dibutyl phosphate, neodymium dipentyl phosphate, neodymiumdihexyl phosphate, neodymium diheptyl phosphate, neodymium dioctylphosphate, neodymium bis(1-methylheptyl) phosphate, neodymiumbis(2-ethylhexyl) phosphate, neodymium didecyl phosphate, neodymiumdidodecyl phosphate, neodymium dioctadecyl phosphate, neodymium dioleylphosphate, neodymium diphenyl phosphate, neodymium bis(p-nonylphenyl)phosphate, neodymium butyl (2-ethylhexyl) phosphate, neodymium(1-methylheptyl) (2-ethylhexyl) phosphate, and neodymium (2-ethylhexyl)(p-nonylphenyl) phosphate.

Suitable neodymium organophosphonates include, but are not limited to,neodymium butyl phosphonate, neodymium pentyl phosphonate, neodymiumhexyl phosphonate, neodymium heptyl phosphonate, neodymium octylphosphonate, neodymium (1-methylheptyl) phosphonate, neodymium(2-ethylhexyl) phosphonate, neodymium decyl phosphonate, neodymiumdodecyl phosphonate, neodymium octadecyl phosphonate, neodymium oleylphosphonate, neodymium phenyl phosphonate, neodymium (p-nonylphenyl)phosphonate, neodymium butyl butylphosphonate, neodymium pentylpentylphosphonate, neodymium hexyl hexylphosphonate, neodymium heptylheptylphosphonate, neodymium octyl octylphosphonate, neodymium(1-methylheptyl) (1-methylheptyl) phosphonate, neodymium (2-ethylhexyl)(2-ethylhexyl)phosphonate, neodymium decyl decylphosphonate, neodymiumdodecyl dodecylphosphonate, neodymium octadecyl octadecylphosphonate,neodymium oleyl oleylphosphonate, neodymium phenyl phenylphosphonate,neodymium (p-nonylphenyl) (p-nonylphenyl) phosphonate, neodymium butyl(2-ethylhexyl)phosphonate, neodymium (2-ethylhexyl) butylphosphonate,neodymium (1-methylheptyl) (2-ethylhexyl)phosphonate, neodymium(2-ethylhexyl) (1-methylheptyl)phosphonate, neodymium (2-ethylhexyl)(p-nonylphenyl)phosphonate, and neodymium (p-nonylphenyl)(2-ethylhexyl)phosphonate.

Suitable neodymium organophosphinates include, but are not limited to,neodymium butylphosphinate, neodymium pentylphosphinate, neodymiumhexylphosphinate, neodymium heptylphosphinate, neodymiumoctylphosphinate, neodymium (1-methylheptyl)phosphinate, neodymium(2-ethylhexyl)phosphinate, neodymium decylphosphinate, neodymiumdodecylphosphinate, neodymium octadecylphosphinate, neodymiumoleylphosphinate, neodymium phenylphosphinate, neodymium(p-nonylphenyl)phosphinate, neodymium dibutylphosphinate, neodymiumdipentylphosphinate, neodymium dihexylphosphinate, neodymiumdiheptylphosphinate, neodymium dioctylphosphinate, neodymiumbis(1-methylheptyl)phosphinate, neodymium bis(2-ethylhexyl)phosphinate,neodymium didecylphosphinate, neodymium didodecylphosphinate, neodymiumdioctadecylphosphinate, neodymium dioleylphosphinate, neodymiumdiphenylphosphinate, neodymium bis(p-nonylphenyl) phosphinate, neodymiumbutyl (2-ethylhexyl) phosphinate, neodymium (1-methylheptyl)(2-ethylhexyl)phosphinate, and neodymium (2-ethylhexyl) (p-nonylphenyl)phosphinate.

Suitable neodymium carbamates include, but are not limited to, neodymiumdimethylcarbamate, neodymium diethylcarbamate, neodymiumdiisopropylcarbamate, neodymium dibutylcarbamate, and neodymiumdibenzylcarbamate.

Suitable neodymium dithiocarbamates include, but are not limited to,neodymium dimethyldithiocarbamate, neodymium diethyldithiocarbamate,neodymium diisopropyldithiocarbamate, neodymium dibutyldithiocarbamate,and neodymium dibenzyldithiocarbamate.

Suitable neodymium xanthates include, but are not limited to, neodymiummethylxanthate, neodymium ethylxanthate, neodymium isopropylxanthate,neodymium butylxanthate, and neodymium benzylxanthate.

Suitable neodymium β-diketonates include, but are not limited to,neodymium acetylacetonate, neodymium trifluoroacetylacetonate, neodymiumhexafluoroacetylacetonate, neodymium benzoylacetonate, and neodymium2,2,6,6-tetramethyl-3,5-heptanedionate.

Suitable neodymium alkoxides or aryloxides include, but are not limitedto, neodymium methoxide, neodymium ethoxide, neodymium isopropoxide,neodymium 2-ethylhexoxide, neodymium phenoxide, neodymiumnonylphenoxide, and neodymium naphthoxide.

Suitable neodymium halides include, but are not limited to, neodymiumfluoride, neodymium chloride, neodymium bromide, and neodymium iodide.Suitable neodymium pseudo-halides include, but are not limited to,neodymium cyanide, neodymium cyanate, neodymium thiocyanate, neodymiumazide, and neodymium ferrocyanide. Suitable neodymium oxyhalidesinclude, but are not limited to, neodymium oxyfluoride, neodymiumoxychloride, and neodymium oxybromide. A Lewis base, such astetrahydrofuran (“THF”), may be employed as an aid for solubilizing thisclass of neodymium compounds in inert organic solvents. Where lanthanidehalides, lanthanide oxyhalides, or other lanthanide-containing compoundscontaining a halogen atom are employed, the lanthanide-containingcompound may optionally also provide all or part of the halogen sourcein the lanthanide-based catalyst system.

As used herein, the term organolanthanide compound refers to anylanthanide-containing compound containing at least one lanthanide-carbonbond. These compounds are predominantly, though not exclusively, thosecontaining cyclopentadienyl (“Cp”), substituted cyclopentadienyl, allyl,and substituted allyl ligands. Suitable organolanthanide compoundsinclude, but are not limited to, Cp₃Ln, Cp₂LnR, Cp₂LnCl, CpLnCl₂,CpLn(cyclooctatetraene), (C₅Me₅)₂LnR, LnR₃, Ln(allyl)₃, andLn(allyl)₂Cl, where Ln represents a lanthanide atom, and R represents ahydrocarbyl group. In one or more embodiments, hydrocarbyl groups usefulin the present invention may contain heteroatoms such as, for example,nitrogen, oxygen, boron, silicon, sulfur, and phosphorus atoms.

Alkylating Agents

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include an alkylating agent. In one or moreembodiments, alkylating agents, which may also be referred to ashydrocarbylating agents, include organometallic compounds that cantransfer one or more hydrocarbyl groups to another metal. Generally,these agents include organometallic compounds of electropositive metalssuch as Groups 1, 2, and 3 metals (Groups IA, IIA, and IIIA metals).Alkylating agents useful in the present invention include, but are notlimited to, organoaluminum and organomagnesium compounds. As usedherein, the term organoaluminum compound refers to any aluminum compoundcontaining at least one aluminum-carbon bond. In one or moreembodiments, organoaluminum compounds that are soluble in a hydrocarbonsolvent can be employed. As used herein, the term organomagnesiumcompound refers to any magnesium compound that contains at least onemagnesium-carbon bond. In one or more embodiments, organomagnesiumcompounds that are soluble in a hydrocarbon can be employed. As will bedescribed in more detail below, several species of suitable alkylatingagents can be in the form of a halide. Where the alkylating agentincludes a halogen atom, the alkylating agent may also serve as all orpart of the halogen source in the above-mentioned catalyst system.

Organoaluminum Compounds

In one or more embodiments, organoaluminum compounds that can beutilized in the lanthanide-based catalyst system include thoserepresented by the general formula AlR_(n)X_(3-n), where each Rindependently can be a monovalent organic group that is attached to thealuminum atom via a carbon atom, where each X independently can be ahydrogen atom, a halogen atom, a carboxylate group, an alkoxide group,or an aryloxide group, and where n can be an integer in the range offrom 1 to 3. In one or more embodiments, each R independently can be ahydrocarbyl group such as, for example, alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,substituted aryl, aralkyl, alkaryl, allyl, and alkynyl groups, with eachgroup containing in the range of from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms. These hydrocarbyl groups may contain heteroatoms including, butnot limited to, nitrogen, oxygen, boron, silicon, sulfur, and phosphorusatoms.

Types of the organoaluminum compounds that are represented by thegeneral formula AlR_(n)X_(3-n) include, but are not limited to,trihydrocarbylaluminum, dihydrocarbylaluminum hydride,hydrocarbylaluminum dihydride, dihydrocarbylaluminum carboxylate,hydrocarbylaluminum bis(carboxylate), dihydrocarbylaluminum alkoxide,hydrocarbylaluminum dialkoxide, dihydrocarbylaluminum halide,hydrocarbylaluminum dihalide, dihydrocarbylaluminum aryloxide, andhydrocarbylaluminum diaryloxide compounds. In one embodiment, thealkylating agent can comprise trihydrocarbylaluminum,dihydrocarbylaluminum hydride, and/or hydrocarbylaluminum dihydridecompounds. In one embodiment, when the alkylating agent includes anorganoaluminum hydride compound, the above-mentioned halogen source canbe provided by a tin halide, as disclosed in U.S. Pat. No. 7,008,899,which is incorporated herein by reference in its entirety.

Suitable trihydrocarbylaluminum compounds include, but are not limitedto, trimethylaluminum, triethylaluminum, triisobutylaluminum,tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum,tri-t-butylaluminum, tri-n-pentylaluminum, trineopentylaluminum,tri-n-hexylaluminum, tri-n-octylaluminum, tris(2-ethylhexyl)aluminum,tricyclohexylaluminum, tris(1-methylcyclopentyl)aluminum,triphenylaluminum, tri-p-tolylaluminum,tris(2,6-dimethylphenyl)aluminum, tribenzylaluminum,diethylphenylaluminum, diethyl-p-tolylaluminum, diethylbenzylaluminum,ethyldiphenylaluminum, ethyldi-p-tolylaluminum, andethyldibenzylaluminum.

Suitable dihydrocarbylaluminum hydride compounds include, but are notlimited to, diethylaluminum hydride, di-n-propylaluminum hydride,diisopropylaluminum hydride, di-n-butylaluminum hydride,diisobutylaluminum hydride, di-n-octylaluminum hydride, diphenylaluminumhydride, di-p-tolylaluminum hydride, dibenzylaluminum hydride,phenylethylaluminum hydride, phenyl-n-propylaluminum hydride,phenylisopropylaluminum hydride, phenyl-n-butylaluminum hydride,phenylisobutylaluminum hydride, phenyl-n-octylaluminum hydride,p-tolylethylaluminum hydride, p-tolyl-n-propylaluminum hydride,p-tolylisopropylaluminum hydride, p-tolyl-n-butylaluminum hydride,p-tolylisobutylaluminum hydride, p-tolyl-n-octylaluminum hydride,benzylethylaluminum hydride, benzyl-n-propylaluminum hydride,benzylisopropylaluminum hydride, benzyl-n-butylaluminum hydride,benzylisobutylaluminum hydride, and benzyl-n-octylaluminum hydride.

Suitable hydrocarbylaluminum dihydrides include, but are not limited to,ethylaluminum dihydride, n-propylaluminum dihydride, isopropylaluminumdihydride, n-butylaluminum dihydride, isobutylaluminum dihydride, andn-octylaluminum dihydride.

Suitable dihydrocarbylaluminum halide compounds include, but are notlimited to, diethylaluminum chloride, di-n-propylaluminum chloride,diisopropylaluminum chloride, di-n-butylaluminum chloride,diisobutylaluminum chloride, di-n-octylaluminum chloride,diphenylaluminum chloride, di-p-tolylaluminum chloride, dibenzylaluminumchloride, phenylethylaluminum chloride, phenyl-n-propylaluminumchloride, phenylisopropylaluminum chloride, phenyl-n-butylaluminumchloride, phenylisobutylaluminum chloride, phenyl-n-octylaluminumchloride, p-tolylethylaluminum chloride, p-tolyl-n-propylaluminumchloride, p-tolylisopropylaluminum chloride, p-tolyl-n-butylaluminumchloride, p-tolylisobutylaluminum chloride, p-tolyl-n-octylaluminumchloride, benzylethylaluminum chloride, benzyl-n-propylaluminumchloride, benzylisopropylaluminum chloride, benzyl-n-butylaluminumchloride, benzylisobutylaluminum chloride, and benzyl-n-octylaluminumchloride.

Suitable hydrocarbylaluminum dihalide compounds include, but are notlimited to, ethylaluminum dichloride, n-propylaluminum dichloride,isopropylaluminum dichloride, n-butylaluminum dichloride,isobutylaluminum dichloride, and n-octylaluminum dichloride.

Other organoaluminum compounds useful as alkylating agents that may berepresented by the general formula AlR_(n)X_(3-n) include, but are notlimited to, dimethylaluminum hexanoate, diethylaluminum octoate,diisobutylaluminum 2-ethylhexanoate, dimethylaluminum neodecanoate,diethylaluminum stearate, diisobutylaluminum oleate, methylaluminumbis(hexanoate), ethylaluminum bis(octoate), isobutylaluminumbis(2-ethylhexanoate), methylaluminum bis(neodecanoate), ethylaluminumbis(stearate), isobutylaluminum bis(oleate), dimethylaluminum methoxide,diethylaluminum methoxide, diisobutylaluminum methoxide,dimethylaluminum ethoxide, diethylaluminum ethoxide, diisobutylaluminumethoxide, dimethylaluminum phenoxide, diethylaluminum phenoxide,diisobutylaluminum phenoxide, methylaluminum dimethoxide, ethylaluminumdimethoxide, isobutylaluminum dimethoxide, methylaluminum diethoxide,ethylaluminum diethoxide, isobutylaluminum diethoxide, methylaluminumdiphenoxide, ethylaluminum diphenoxide, and isobutylaluminumdiphenoxide.

Another class of organoaluminum compounds suitable for use as analkylating agent in the lanthanide-based catalyst system isaluminoxanes. Aluminoxanes can comprise oligomeric linear aluminoxanes,which can be represented by the general formula:

and oligomeric cyclic aluminoxanes, which can be represented by thegeneral formula:

where x can be an integer in the range of from 1 to about 100, or about10 to about 50; y can be an integer in the range of from 2 to about 100,or about 3 to about 20; and where each R independently can be amonovalent organic group that is attached to the aluminum atom via acarbon atom. In one embodiment, each R independently can be ahydrocarbyl group including, but not limited to, alkyl, cycloalkyl,substituted cycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl,aryl, substituted aryl, aralkyl, alkaryl, allyl, and alkynyl groups,with each group containing in the range of from 1 carbon atom, or theappropriate minimum number of carbon atoms to form the group, up toabout 20 carbon atoms. These hydrocarbyl groups may also containheteroatoms including, but not limited to, nitrogen, oxygen, boron,silicon, sulfur, and phosphorus atoms. It should be noted that thenumber of moles of the aluminoxane as used in this application refers tothe number of moles of the aluminum atoms rather than the number ofmoles of the oligomeric aluminoxane molecules. This convention iscommonly employed in the art of catalyst systems utilizing aluminoxanes.

Aluminoxanes can be prepared by reacting trihydrocarbylaluminumcompounds with water. This reaction can be performed according to knownmethods, such as, for example, (1) a method in which thetrihydrocarbylaluminum compound is dissolved in an organic solvent andthen contacted with water, (2) a method in which thetrihydrocarbylaluminum compound is reacted with water of crystallizationcontained in, for example, metal salts, or water adsorbed in inorganicor organic compounds, or (3) a method in which thetrihydrocarbylaluminum compound is reacted with water in the presence ofthe monomer or monomer solution that is to be polymerized.

Suitable aluminoxane compounds include, but are not limited to,methylaluminoxane, modified methylaluminoxane, ethylaluminoxane,n-propylaluminoxane, isopropylaluminoxane, butylaluminoxane,isobutylaluminoxane, n-pentylaluminoxane, neopentylaluminoxane,n-hexylaluminoxane, n-octylaluminoxane, 2-ethylhexylaluminoxane,cyclohexylaluminoxane, 1-methylcyclopentylaluminoxane,phenylaluminoxane, and 2,6-dimethylphenylaluminoxane. Modifiedmethylaluminoxane can be formed by substituting about 5 to 95 percent ofthe methyl groups of methylaluminoxane with C₂ to C₁₂ hydrocarbylgroups, preferably with isobutyl groups, by using techniques known tothose skilled in the art.

In one or more embodiments, aluminoxanes can be used alone or incombination with other organoaluminum compounds. In one embodiment,methylaluminoxane and at least one other organoaluminum compound (e.g.,AlR_(n)X_(3-n)), such as diisobutyl aluminum hydride, can be employed incombination. U.S. Publication No. 2008/0182954, which is incorporatedherein by reference in its entirety, provides other examples wherealuminoxanes and organoaluminum compounds can be employed incombination. In one or more embodiments, the catalyst compositionsemployed in the present invention are devoid or substantially devoid ofaluminoxanes.

Organomagnesium Compounds

As mentioned above, alkylating agents useful in the lanthanide-basedcatalyst system can include organomagnesium compounds. In one or moreembodiments, organomagnesium compounds that can be utilized includethose represented by the general formula MgR₂, where each Rindependently can be a monovalent organic group that is attached to themagnesium atom via a carbon atom. In one or more embodiments, each Rindependently can be a hydrocarbyl group including, but not limited to,alkyl, cycloalkyl, substituted cycloalkyl, alkenyl, cycloalkenyl,substituted cycloalkenyl, aryl, allyl, substituted aryl, aralkyl,alkaryl, and alkynyl groups, with each group containing in the range offrom 1 carbon atom, or the appropriate minimum number of carbon atoms toform the group, up to about 20 carbon atoms. These hydrocarbyl groupsmay also contain heteroatoms including, but not limited to, nitrogen,oxygen, silicon, sulfur, and phosphorus atoms.

Suitable organomagnesium compounds that may be represented by thegeneral formula MgR₂ include, but are not limited to, diethylmagnesium,di-n-propylmagnesium, diisopropylmagnesium, dibutylmagnesium,dihexylmagnesium, diphenylmagnesium, and dibenzylmagnesium.

Another class of organomagnesium compounds that can be utilized as analkylating agent may be represented by the general formula RMgX, where Rcan be a monovalent organic group that is attached to the magnesium atomvia a carbon atom, and X can be a hydrogen atom, a halogen atom, acarboxylate group, an alkoxide group, or an aryloxide group. Where thealkylating agent is an organomagnesium compound that includes a halogenatom, the organomagnesium compound can serve as both the alkylatingagent and at least a portion of the halogen source in the catalystsystems. In one or more embodiments, R can be a hydrocarbyl groupincluding, but not limited to, alkyl, cycloalkyl, substitutedcycloalkyl, alkenyl, cycloalkenyl, substituted cycloalkenyl, aryl,allyl, substituted aryl, aralkyl, alkaryl, and alkynyl groups, with eachgroup containing in the range of from 1 carbon atom, or the appropriateminimum number of carbon atoms to form the group, up to about 20 carbonatoms. These hydrocarbyl groups may also contain heteroatoms including,but not limited to, nitrogen, oxygen, boron, silicon, sulfur, andphosphorus atoms. In one embodiment, X can be a carboxylate group, analkoxide group, or an aryloxide group, with each group containing in therange of from 1 to about 20 carbon atoms.

Types of organomagnesium compounds that may be represented by thegeneral formula RMgX include, but are not limited to,hydrocarbylmagnesium hydride, hydrocarbylmagnesium halide,hydrocarbylmagnesium carboxylate, hydrocarbylmagnesium alkoxide, andhydrocarbylmagnesium aryloxide.

Suitable organomagnesium compounds that may be represented by thegeneral formula RMgX include, but are not limited to, methylmagnesiumhydride, ethylmagnesium hydride, butylmagnesium hydride, hexylmagnesiumhydride, phenylmagnesium hydride, benzylmagnesium hydride,methylmagnesium chloride, ethylmagnesium chloride, butylmagnesiumchloride, hexylmagnesium chloride, phenylmagnesium chloride,benzylmagnesium chloride, methylmagnesium bromide, ethylmagnesiumbromide, butylmagnesium bromide, hexylmagnesium bromide, phenylmagnesiumbromide, benzylmagnesium bromide, methylmagnesium hexanoate,ethylmagnesium hexanoate, butylmagnesium hexanoate, hexylmagnesiumhexanoate, phenylmagnesium hexanoate, benzylmagnesium hexanoate,methylmagnesium ethoxide, ethylmagnesium ethoxide, butylmagnesiumethoxide, hexylmagnesium ethoxide, phenylmagnesium ethoxide,benzylmagnesium ethoxide, methylmagnesium phenoxide, ethylmagnesiumphenoxide, butylmagnesium phenoxide, hexylmagnesium phenoxide,phenylmagnesium phenoxide, and benzylmagnesium phenoxide.

Halogen Sources

As mentioned above, the lanthanide-based catalyst systems employed inthe present invention can include a halogen source. As used herein, theterm halogen source refers to any substance including at least onehalogen atom. In one or more embodiments, at least a portion of thehalogen source can be provided by either of the above-describedlanthanide-containing compound and/or the above-described alkylatingagent, when those compounds contain at least one halogen atom. In otherwords, the lanthanide-containing compound can serve as both thelanthanide-containing compound and at least a portion of the halogensource. Similarly, the alkylating agent can serve as both the alkylatingagent and at least a portion of the halogen source.

In another embodiment, at least a portion of the halogen source can bepresent in the catalyst systems in the form of a separate and distincthalogen-containing compound. Various compounds, or mixtures thereof,that contain one or more halogen atoms can be employed as the halogensource. Examples of halogen atoms include, but are not limited to,fluorine, chlorine, bromine, and iodine. A combination of two or morehalogen atoms can also be utilized. Halogen-containing compounds thatare soluble in a hydrocarbon solvent are suitable for use in the presentinvention. Hydrocarbon-insoluble halogen-containing compounds, however,can be suspended in a polymerization system to form the catalyticallyactive species, and are therefore also useful.

Useful types of halogen-containing compounds that can be employedinclude, but are not limited to, elemental halogens, mixed halogens,hydrogen halides, organic halides, inorganic halides, metallic halides,and organometallic halides.

Suitable elemental halogens include, but are not limited to, fluorine,chlorine, bromine, and iodine. Some specific examples of suitable mixedhalogens include iodine monochloride, iodine monobromide, iodinetrichloride, and iodine pentafluoride.

Suitable hydrogen halides include, but are not limited to, hydrogenfluoride, hydrogen chloride, hydrogen bromide, and hydrogen iodide.

Suitable organic halides include, but are not limited to, t-butylchloride, t-butyl bromide, allyl chloride, allyl bromide, benzylchloride, benzyl bromide, chloro-di-phenylmethane,bromo-di-phenylmethane, triphenylmethyl chloride, triphenylmethylbromide, benzylidene chloride, benzylidene bromide,methyltrichlorosilane, phenyltrichlorosilane, dimethyldichlorosilane,diphenyldichlorosilane, trimethylchlorosilane, benzoyl chloride, benzoylbromide, propionyl chloride, propionyl bromide, methyl chloroformate,and methyl bromoformate.

Suitable inorganic halides include, but are not limited to, phosphorustrichloride, phosphorus tribromide, phosphorus pentachloride, phosphorusoxychloride, phosphorus oxybromide, boron trifluoride, borontrichloride, boron tribromide, silicon tetrafluoride, silicontetrachloride, silicon tetrabromide, silicon tetraiodide, arsenictrichloride, arsenic tribromide, arsenic triiodide, seleniumtetrachloride, selenium tetrabromide, tellurium tetrachloride, telluriumtetrabromide, and tellurium tetraiodide.

Suitable metallic halides include, but are not limited to, tintetrachloride, tin tetrabromide, aluminum trichloride, aluminumtribromide, antimony trichloride, antimony pentachloride, antimonytribromide, aluminum triiodide, aluminum trifluoride, galliumtrichloride, gallium tribromide, gallium triiodide, gallium trifluoride,indium trichloride, indium tribromide, indium triiodide, indiumtrifluoride, titanium tetrachloride, titanium tetrabromide, titaniumtetraiodide, zinc dichloride, zinc dibromide, zinc diiodide, and zincdifluoride.

Suitable organometallic halides include, but are not limited to,dimethylaluminum chloride, diethylaluminum chloride, dimethylaluminumbromide, diethylaluminum bromide, dimethylaluminum fluoride,diethylaluminum fluoride, methylaluminum dichloride, ethylaluminumdichloride, methylaluminum dibromide, ethylaluminum dibromide,methylaluminum difluoride, ethylaluminum difluoride, methylaluminumsesquichloride, ethylaluminum sesquichloride, isobutylaluminumsesquichloride, methylmagnesium chloride, methylmagnesium bromide,methylmagnesium iodide, ethylmagnesium chloride, ethylmagnesium bromide,butylmagnesium chloride, butylmagnesium bromide, phenylmagnesiumchloride, phenylmagnesium bromide, benzylmagnesium chloride,trimethyltin chloride, trimethyltin bromide, triethyltin chloride,triethyltin bromide, di-t-butyltin dichloride, di-t-butyltin dibromide,dibutyltin dichloride, dibutyltin dibromide, tributyltin chloride, andtributyltin bromide.

Non-Coordinating Anion/Non-Coordinating Anion Precursor

In one or more embodiments, the lanthanide-based catalyst systems cancomprise a compound containing a non-coordinating anion or anon-coordinating anion precursor. In one or more embodiments, a compoundcontaining a non-coordinating anion, or a non-coordinating anionprecursor can be employed in lieu of the above-described halogen source.A non-coordinating anion is a sterically bulky anion that does not formcoordinate bonds with, for example, the active center of a catalystsystem due to steric hindrance. Non-coordinating anions useful in thepresent invention include, but are not limited to, tetraarylborateanions and fluorinated tetraarylborate anions. Compounds containing anon-coordinating anion can also contain a counter cation, such as acarbonium, ammonium, or phosphonium cation. Exemplary counter cationsinclude, but are not limited to, triarylcarbonium cations andN,N-dialkylanilinium cations. Examples of compounds containing anon-coordinating anion and a counter cation include, but are not limitedto, triphenylcarbonium tetrakis(pentafluorophenyl)borate,N,N-dimethylanilinium tetrakis(pentafluorophenyl)borate,triphenylcarbonium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate, andN,N-dimethylanilinium tetrakis [3,5-bis(trifluoromethyl)phenyl]borate.

A non-coordinating anion precursor can also be used in this embodiment.A non-coordinating anion precursor is a compound that is able to form anon-coordinating anion under reaction conditions. Usefulnon-coordinating anion precursors include, but are not limited to,triarylboron compounds, BR₃, where R is a strong electron-withdrawingaryl group, such as a pentafluorophenyl or3,5-bis(trifluoromethyl)phenyl group.

The lanthanide-based catalyst composition used in this invention may beformed by combining or mixing the foregoing catalyst ingredients.Although one or more active catalyst species are believed to result fromthe combination of the lanthanide-based catalyst ingredients, the degreeof interaction or reaction between the various catalyst ingredients orcomponents is not known with any great degree of certainty. Therefore,the term “catalyst composition” has been employed to encompass a simplemixture of the ingredients, a complex of the various ingredients that iscaused by physical or chemical forces of attraction, a chemical reactionproduct of the ingredients, or a combination of the foregoing.

Amounts

The foregoing lanthanide-based catalyst composition may have highcatalytic activity for polymerizing conjugated dienes intocis-1,4-polydienes over a wide range of catalyst concentrations andcatalyst ingredient ratios. Several factors may impact the optimumconcentration of any one of the catalyst ingredients. For example,because the catalyst ingredients may interact to form an active species,the optimum concentration for any one catalyst ingredient may bedependent upon the concentrations of the other catalyst ingredients.

In one or more embodiments, the molar ratio of the alkylating agent tothe lanthanide-containing compound (alkylating agent/Ln) can be variedfrom about 1:1 to about 1,000:1, in other embodiments from about 2:1 toabout 500:1, and in other embodiments from about 5:1 to about 200:1.

In those embodiments where both an aluminoxane and at least one otherorganoaluminum agent are employed as alkylating agents, the molar ratioof the aluminoxane to the lanthanide-containing compound(aluminoxane/Ln) can be varied from 5:1 to about 1,000:1, in otherembodiments from about 10:1 to about 700:1, and in other embodimentsfrom about 20:1 to about 500:1; and the molar ratio of the at least oneother organoaluminum compound to the lanthanide-containing compound(Al/Ln) can be varied from about 1:1 to about 200:1, in otherembodiments from about 2:1 to about 150:1, and in other embodiments fromabout 5:1 to about 100:1.

The molar ratio of the halogen-containing compound to thelanthanide-containing compound is best described in terms of the ratioof the moles of halogen atoms in the halogen source to the moles oflanthanide atoms in the lanthanide-containing compound (halogen/Ln). Inone or more embodiments, the halogen/Ln molar ratio can be varied fromabout 0.5:1 to about 20:1, in other embodiments from about 1:1 to about10:1, and in other embodiments from about 2:1 to about 6:1.

In yet another embodiment, the molar ratio of the non-coordinating anionor non-coordinating anion precursor to the lanthanide-containingcompound (An/Ln) may be from about 0.5:1 to about 20:1, in otherembodiments from about 0.75:1 to about 10:1, and in other embodimentsfrom about 1:1 to about 6:1.

Preparation of Catalyst System

The catalyst systems employed in the present invention can be formed byvarious methods.

In one or more embodiments, the lanthanide-based catalyst compositionmay be formed in situ by adding the catalyst ingredients to a solutioncontaining monomer and solvent, or to bulk monomer, in either a stepwiseor simultaneous manner. In one embodiment, the alkylating agent can beadded first, followed by the lanthanide-containing compound, and thenfollowed by the halogen source or by the compound containing anon-coordinating anion or the non-coordinating anion precursor.

In one or more embodiments, the lanthanide-based catalyst compositionmay be preformed. That is, the catalyst ingredients are premixed outsidethe polymerization system. In one or more embodiments, the premixing ofthe catalyst ingredients forms an active catalyst system, which is acatalyst system capable of polymerizing monomer, especially conjugateddiene monomer into the desired cis-1,4-polydienes desired by one or moreembodiments of this invention. Examples of useful processes forpreforming a lanthanide-based catalyst composition are disclosed in U.S.Pat. Nos. 5,686,371, 6,576,731, U.S. Pat. Pub. No. 2002/0,035,226, U.S.Pat. Pub. No. 2012/0,208,964, and U.S. Pat. Pub. No. 2013/0,237,669,which are incorporated herein by reference.

Order of Addition

In one or more embodiments, the catalyst system may be formed bycombining the catalyst ingredients simultaneously or sequentially. Wherethe ingredients are combined sequentially, the alkylating agent can befirst combined with the lanthanide-containing compound, and then themixture can be combined with the halogen source or the compoundcontaining a non-coordinating anion or the non-coordinating anionprecursor. In other embodiments, the alkylating agent and the halogensource (or non-coordinating anion or non-coordinating anion precursor)can first be combined, and then the mixture can be combined with thelanthanide-containing compound. In yet other embodiments, thelanthanide-containing compound and the halogen source (ornon-coordinating anion or non-coordinating anion precursor) can first becombined, and then the mixture can be combined with the alkylatingagent.

Use of Solvent

In one or more embodiments, a solvent may be employed as a carrier toeither dissolve or suspend the catalyst in order to facilitate thedelivery of the catalyst to the polymerization system. In otherembodiments, monomer can be used as the carrier. In yet otherembodiments, the catalyst or initiator can be used in their neat statewithout any solvent.

In one or more embodiments, where the catalyst is preformed. In one ormore embodiments, the preformation of the catalyst may take place with asolvent. In one or more embodiments, a solvent may be employed as acarrier to either dissolve or suspend the catalyst in order tofacilitate the delivery of the catalyst to the polymerization system. Inother embodiments, monomer can be used as the carrier. In yet otherembodiments, the catalyst can be used in their neat state without anysolvent.

In one or more embodiments, suitable solvents include those organiccompounds that will not undergo polymerization or incorporation intopropagating polymer chains during the polymerization of monomer in thepresence of the catalyst or initiator. In one or more embodiments, theseorganic species are liquid at ambient temperature and pressure. In oneor more embodiments, these organic solvents are inert to the catalyst orinitiator. Exemplary organic solvents include hydrocarbons with a low orrelatively low boiling point such as aromatic hydrocarbons, aliphatichydrocarbons, and cycloaliphatic hydrocarbons. Non-limiting examples ofaromatic hydrocarbons include benzene, toluene, xylenes, ethylbenzene,diethylbenzene, and mesitylene. Non-limiting examples of aliphatichydrocarbons include n-pentane, n-hexane, n-heptane, n-octane, n-nonane,n-decane, isopentane, isohexanes, isopentanes, isooctanes,2,2-dimethylbutane, petroleum ether, kerosene, and petroleum spirits.And, non-limiting examples of cycloaliphatic hydrocarbons includecyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane.Mixtures of the above hydrocarbons may also be used. As is known in theart, aliphatic and cycloaliphatic hydrocarbons may be desirably employedfor environmental reasons. The low-boiling hydrocarbon solvents aretypically separated from the polymer upon completion of thepolymerization.

Other examples of organic solvents include high-boiling hydrocarbons ofhigh molecular weights, including hydrocarbon oils that are commonlyused to oil-extend polymers. Examples of these oils include paraffinicoils, aromatic oils, naphthenic oils, vegetable oils other than castoroils, and low PCA oils including MES, TDAE, SRAE, heavy naphthenic oils.Since these hydrocarbons are non-volatile, they typically do not requireseparation and remain incorporated in the polymer.

Use of Stabilizers

In one or more embodiments, the catalyst system may optionally beprepared in the presence of a small amount of an alkene containingcompound, which may serve to stabilize the catalyst system. Usefulalkene containing compounds may include monomer as defined herein.Specific examples of suitable monomers for stabilizing the catalystsystem include conjugated diene monomers such as 1,3-butadiene orisoprene. The amount of alkene containing compound that may be used forstabilizing the catalyst can range from about 1 to about 500 moles, inother embodiments from about 2 to about 250 moles, in other embodimentsfrom about 3 to about 100 moles, in other embodiments from about 5 toabout 500 moles, and in other embodiments from about 10 to about 20moles per mole of the lanthanide-containing compound.

Conditions for Forming Catalyst System

In one or more embodiments, the catalyst systems used in this inventionmay be prepared at specific temperatures. In one or more embodiments,the catalyst compositions can be prepared at a temperature of at least−20° C., in other embodiments at least 0° C., in other embodiments atleast 20° C., and in other embodiments at least 40° C. In these or otherembodiments, the catalyst compositions can be prepared at a temperatureof at most 100° C., in other embodiments at most 80° C., in otherembodiments at most 60° C., in other embodiments at most 40° C., inother embodiments at most 20° C., and in other embodiments at most 0° C.

Catalyst System Aging

In one or more embodiments, the catalyst composition may be aged priorto use (i.e. prior to being added to the polymerization system).

In one or more embodiments, the catalyst composition may be aged at atemperature of at least −20° C., in other embodiments at least 0° C., inother embodiments at least 20° C., and in other embodiments at least 40°C. In these or other embodiments, the catalyst compositions may be agedat a temperature of at most 100° C., in other embodiments at most 80°C., in other embodiments at most 60° C., in other embodiments at most40° C., in other embodiments at most 20° C., and in other embodiments atmost 0° C. In certain embodiments, the catalyst composition may be agedin an environment without temperature control, where the catalystcomposition would potentially be subject to varying environmentaltemperatures. In these or other embodiments, the catalyst compositionmay be aged at a temperature as described above and further aged, for atleast a portion of the aging time, at an uncontrolled temperature.

In one or more embodiments, the catalyst composition may be aged for atleast 10 minutes, in other embodiments at least 30 minutes, in otherembodiments at least 1 hour, in other embodiments at least 3 hours, inother embodiments at least 6 hours, in other embodiments at least 12hours, in other embodiments at least 24 hours, in other embodiments atleast 6 days, in other embodiments at least 12 days, in otherembodiments at least 30 days, and in other embodiments at least 60 days.In these or other embodiments, the catalyst compositions may be aged forat most 1000 days, in other embodiments at most 750 days, in otherembodiments at most 500 days, in other embodiments at most 300 days, andin other embodiments at most 100 days, in other embodiments at most 24days, in other embodiments at most 18 days, and in other embodiments atmost 12 days. In one or more embodiments, the catalyst composition isaged from about 4 to about 16 days, in other embodiments from about 5 toabout 15 days, and in other embodiments from about 6 to about 12 days.

Specific Catalyst Systems

In one or more embodiments, the catalyst employed in the practice ofthis invention is a preformed catalyst that is the combination orreaction product of a lanthanide carboxylate, an aluminum hydride, andan organometallic halide. In specific embodiments, the lanthanidecarboxylate is a neodymium carboxylate, the aluminum hydride is adihydrocarbylaluminum hydride and/or hydrocarbylaluminum dihydride, andthe organometallic halide is a hydrocarbyl aluminum sesquichloride. Instill more specific embodiments, the catalyst system is the combinationor reaction product of a neodymium neodecanoate, diisobutylaluminumhydride, and ethylaluminum sesquichloride. The catalyst system may havea diisobutylaluminum hydride to neodymium neodecanoate molar ratio fromabout 5 to about 40, or in other embodiments from about 10 to about 20,and an ethylaluminum sesquichloride to neodymium neodecanoate molarratio, which is best described as a molar ratio of the moles of halogenatoms in the ethylaluminum sesquichloride to the moles of lanthanideatoms in the neodymium neodecanoate (halogen/Ln), of from about 1 toabout 4, or in other embodiments from about 2 to about 3. In these orother embodiments, these specific catalyst systems may include aconjugated diene (such as 1,3-butadiene or isoprene) as a stabilizer. Inyet still more specific embodiments, the recited specific catalystsystems are aged as described herein.

Catalyst systems that may be employed in one or more embodiments of thisinvention are commercially available. For example, useful preformedcatalyst systems are available under the tradename COMCAT Nd-FC (NH),COMCAT Nd-FC/20 (NH), COMCAT Nd-FC/SF [COMAR CHEMICALS (Pty) Ltd].

Polymerization Mixture

The production of the reactive polymer according to this invention canbe accomplished by polymerizing conjugated diene monomer in an amountsufficient to prepare a polymer of a desired molecular weight in thepresence of a catalytically effective amount of the catalyst. Theintroduction of the catalyst and the conjugated diene monomer forms apolymerization mixture, which may also be referred to as polymerizationsystem, in which a reactive polymer is formed. The amount of thecatalyst to be employed may depend on the interplay of various factorssuch as the type of catalyst or initiator employed, the purity of theingredients, the polymerization temperature, the polymerization rate andconversion desired, the molecular weight desired, and many otherfactors. Accordingly, a specific catalyst or initiator amount cannot bedefinitively set forth except to say that catalytically effectiveamounts of the catalyst or initiator may be used.

In one or more embodiments, the amount of the coordinating metalcompound (e.g., a lanthanide-containing compound) used can be variedfrom about 0.001 to about 2 mmol, in other embodiments from about 0.005to about 1 mmol, and in still other embodiments from about 0.01 to about0.2 mmol per 100 gram of monomer.

In one or more embodiments, the polymerization may be carried out in apolymerization system that includes a substantial amount of solvent. Inone embodiment, a solution polymerization system may be employed inwhich both the monomer to be polymerized and the polymer formed aresoluble in the solvent. In another embodiment, a precipitationpolymerization system may be employed by choosing a solvent in which thepolymer formed is insoluble. In both cases, an amount of solvent inaddition to the amount of solvent that may be used in preparing thecatalyst or initiator is usually added to the polymerization system. Theadditional solvent may be the same as or different from the solvent usedin preparing the catalyst or initiator. Exemplary solvents have been setforth above. In one or more embodiments, the solvent content of thepolymerization mixture may be more than 20% by weight, in otherembodiments more than 50% by weight, and in still other embodiments morethan 80% by weight based on the total weight of the polymerizationmixture.

In other embodiments, the polymerization system employed may begenerally considered a bulk polymerization system that includessubstantially no solvent or a minimal amount of solvent. Those skilledin the art will appreciate the benefits of bulk polymerization processes(i.e., processes where monomer acts as the solvent), and therefore thepolymerization system includes less solvent than will deleteriouslyimpact the benefits sought by conducting bulk polymerization. In one ormore embodiments, the solvent content of the polymerization mixture maybe less than about 20% by weight, in other embodiments less than about10% by weight, and in still other embodiments less than about 5% byweight based on the total weight of the polymerization mixture. Inanother embodiment, the polymerization mixture contains no solventsother than those that are inherent to the raw materials employed. Instill another embodiment, the polymerization mixture is substantiallydevoid of solvent, which refers to the absence of that amount of solventthat would otherwise have an appreciable impact on the polymerizationprocess. Polymerization systems that are substantially devoid of solventmay be referred to as including substantially no solvent. In particularembodiments, the polymerization mixture is devoid of solvent.

The polymerization may be conducted in any conventional polymerizationvessels known in the art. In one or more embodiments, solutionpolymerization can be conducted in a conventional stirred-tank reactor.In other embodiments, bulk polymerization can be conducted in aconventional stirred-tank reactor, especially if the monomer conversionis less than about 60%. In still other embodiments, especially where themonomer conversion in a bulk polymerization process is higher than about60%, which typically results in a highly viscous cement, the bulkpolymerization may be conducted in an elongated reactor in which theviscous cement under polymerization is driven to move by piston, orsubstantially by piston. For example, extruders in which the cement ispushed along by a self-cleaning single-screw or double-screw agitatorare suitable for this purpose. Examples of useful bulk polymerizationprocesses are disclosed in U.S. Pat. No. 7,351,776, which isincorporated herein by reference.

In one or more embodiments, all of the ingredients used for thepolymerization can be combined within a single vessel (e.g., aconventional stirred-tank reactor), and all steps of the polymerizationprocess can be conducted within this vessel. In other embodiments, twoor more of the ingredients can be pre-combined in one vessel and thentransferred to another vessel where the polymerization of monomer (or atleast a major portion thereof) may be conducted.

The polymerization can be carried out as a batch process, a continuousprocess, or a semi-continuous process. In the semi-continuous process,the monomer is intermittently charged as needed to replace that monomeralready polymerized. In one or more embodiments, the conditions underwhich the polymerization proceeds may be controlled to maintain thetemperature of the polymerization mixture within a range from about −10°C. to about 200° C., in other embodiments from about 0° C. to about 150°C., and in other embodiments from about 20° C. to about 100° C. In oneor more embodiments, the heat of polymerization may be removed byexternal cooling by a thermally controlled reactor jacket, internalcooling by evaporation and condensation of the monomer through the useof a reflux condenser connected to the reactor, or a combination of thetwo methods. Also, the polymerization conditions may be controlled toconduct the polymerization under a pressure of from about 0.1 atmosphereto about 50 atmospheres, in other embodiments from about 0.5 atmosphereto about 20 atmosphere, and in other embodiments from about 1 atmosphereto about 10 atmospheres. In one or more embodiments, the pressures atwhich the polymerization may be carried out include those that ensurethat the majority of the monomer is in the liquid phase. In these orother embodiments, the polymerization mixture may be maintained underanaerobic conditions.

Pseudo-Living Polymer

Polymerization catalyzed by a lanthanide-based catalyst producespolymers where some or all of the resulting polymer chains may possessreactive chain ends before the polymerization mixture is quenched. Thus,reference to a reactive polymer refers to a polymer having a reactivechain end. As noted above, the reactive polymer prepared with alanthanide-based catalyst may be referred to as a pseudo-living polymer.In one or more embodiments, a polymerization mixture including reactivepolymer may be referred to as an active polymerization mixture or activepolymerization system. The percentage of polymer chains possessing areactive end depends on various factors such as the type of catalyst orinitiator, the type of monomer, the purity of the ingredients, thepolymerization temperature, the monomer conversion, and many otherfactors. In one or more embodiments, at least about 20% of the polymerchains possess a reactive end, in other embodiments at least about 50%of the polymer chains possess a reactive end, and in still otherembodiments at least about 80% of the polymer chains possess a reactiveend. In any event, the reactive polymer can be treated with a Lewis acidaccording to aspects of this invention.

Functionalization Reaction

In one or more embodiments, the reactive polymer, which includes areactive chain end, may optionally be end functionalized by reacting thereactive chain end with a functionalizing agent. In one or moreembodiments, this functionalization takes place prior to treatment witha Lewis acid. In one or more embodiments, the polydienes of thisinvention are not functionalized.

In one or more embodiments, the optional functionalizing agent may bereacted with the reactive polymer after a desired monomer conversion isachieved but before the polymerization mixture is quenched by aquenching agent. In one or more embodiments, the reaction between thefunctionalizing agent and the reactive polymer may take place within 2hours, in other embodiments within 1 hour, in other embodiments within30 minutes, in other embodiments within 5 minutes, and in otherembodiments within one minute after the peak polymerization temperatureis reached. In one or more embodiments, the reaction between thefunctionalizing agent and the reactive polymer can occur once the peakpolymerization temperature is reached. In other embodiments, thereaction between the functionalizing agent and the reactive polymer canoccur after the reactive polymer has been stored. In one or moreembodiments, the storage of the reactive polymer occurs at roomtemperature or below room temperature under an inert atmosphere. In oneor more embodiments, the reaction between the functionalizing agent andthe reactive polymer may take place at a temperature from about 10° C.to about 150° C., and in other embodiments from about 20° C. to about100° C. The time required for completing the reaction between thefunctionalizing agent and the reactive polymer depends on variousfactors such as the type and amount of the catalyst used to prepare thereactive polymer, the type and amount of the functionalizing agent, aswell as the temperature at which the functionalization reaction isconducted. In one or more embodiments, the reaction between thefunctionalizing agent and the reactive polymer can be conducted forabout 10 to 60 minutes.

In one or more embodiments, the optional functionalizing agent may beintroduced to the polymerization mixture at a location (e.g., within avessel) where the polymerization has been conducted. In otherembodiments, the optional functionalizing agent may be introduced to thepolymerization mixture at a location that is distinct from where thepolymerization has taken place. For example, the optionalfunctionalizing agent may be introduced to the polymerization mixture indownstream vessels including downstream reactors or tanks, in-linereactors or mixers, extruders, or devolatilizers.

Functionalizing Agents

In one or more embodiments, suitable optional functionalizing agentsinclude those compounds that contain groups that may react with thereactive polymers produced in accordance with this invention. Exemplaryfunctionalizing agents include ketones, quinones, aldehydes, amides,esters, isocyanates, isothiocyanates, epoxides, imines, aminoketones,aminothioketones, and acid anhydrides. Examples of these compounds aredisclosed in U.S. Pat. Nos. 4,906,706, 4,990,573, 5,064,910, 5,567,784,5,844,050, 6,838,526, 6,977,281, and 6,992,147; U.S. Pat. PublicationNos. 2006/0004131 A1, 2006/0025539 A1, 2006/0030677 A1, and 2004/0147694A1; Japanese Patent Application Nos. 05-051406A, 05-059103A, 10-306113A,and 11-035633A; which are incorporated herein by reference. Otherexamples of functionalizing agents include azine compounds as describedin U.S. Pat. No. 7,879,952, hydrobenzamide compounds as disclosed inU.S. Pat. No. 7,671,138, nitro compounds as disclosed in U.S. Pat. No.7,732,534, protected oxime compounds as disclosed in U.S. Pat. No.8,088,868, hetrocyclic nitrile compounds disclosed in U.S. Pat. No.8,314,189, halosilanes containing an amino group disclosed in U.S. Pat.No. 8,258,332, imide compounds containing a protected amino groupdisclosed in U.S. Pat. No. 7,906,592, nitroso compounds disclosed inU.S. Pat. Pub. No. 2010/0168378, amide containing compounds disclosed inU.S. Pat. Pub. No. 2010/0099826, carboxylic or thiocarboxylic esterscontaining a silylated amino group disclosed in U.S. Pat. Pub. No.2011/0077325, polyoxime compounds disclosed in U.S. Pat. Publ No.2011/0152449, polycyano compounds disclosed in U.S. Pat. Pub. No.2011/0288200, nitrile compounds containing a protected amino groupdisclosed in U.S. Pat. Pub. No. 2012/0059112 all of which areincorporated herein by reference.

The amount of the optional functionalizing agent that can be added tothe polymerization mixture to yield a functionalized polymer may dependon various factors including the type and amount of catalyst used tosynthesize the reactive polymer and the desired degree offunctionalization. In one or more embodiments, where the reactivepolymer is prepared by employing a lanthanide-based catalyst, the amountof functionalizing agent employed can be described with reference to thelanthanide metal of the lanthanide-containing compound. For example, themolar ratio of the functionalizing agent to the lanthanide metal may befrom about 1:1 to about 200:1, in other embodiments from about 5:1 toabout 150:1, and in other embodiments from about 10:1 to about 100:1.

Lewis Acid Treatment

According to aspects of the present invention, the reactive polymer istreated with a Lewis acid. In one or more embodiments, a Lewis acid isintroduced to the polymerization system including the reactive polymer(i.e. to the active polymerization mixture). In one or more embodiments,the introduction of the Lewis acid to the active polymerization mixturetakes place after a desired monomer conversion is achieved and beforethe polymerization mixture is quenched by a quenching agent. In one ormore embodiments, the introduction of the Lewis acid to the activepolymerization mixture may take place within 2 hours, in otherembodiments within 1 hour, and in other embodiments within 30 minutes,in other embodiments within 5 minutes, and in other embodiments within 1minute after the peak polymerization temperature is reached. In one ormore embodiments, the introduction of the Lewis acid to the activepolymerization mixture can occur once the peak polymerizationtemperature is reached. In other embodiments, the introduction of theLewis acid to the active polymerization mixture can occur after thereactive polymer has been stored. In one or more embodiments, thestorage of the reactive polymer occurs at room temperature or below roomtemperature under an inert atmosphere. In one or more embodiments, theLewis acid is introduced to a reactive polymer prior to quenching and/orfunctionalization, and therefore the polymer is in a reactive (i.e.pseudo-living) state at the time the Lewis acid is introduced.

As noted above, the polymer may optionally be functionalized. In one ormore embodiments, the introduction of the Lewis acid may be simultaneouswith the introduction of the optional functionalizing agent. In otherembodiments, the Lewis acid may be introduced to the polymerizationmixture after the optional functionalizing agent is introduced andbefore the polymerization mixture is quenched by a quenching agent. Inone or more embodiments, the introduction of the Lewis acid to theactive polymerization mixture may take place within 2 hours, in otherembodiments within 1 hour, in other embodiments within 30 minutes, inother embodiments within 5 minutes, and in other embodiments within oneminute after the introduction of the optional functionalizing agent.

In one or more embodiments, the introduction of the Lewis acid to theactive polymerization mixture may take place at a temperature from about10° C. to about 150° C., and in other embodiments from about 20° C. toabout 100° C. The time required for allowing any reaction or interactionthat may take place between the Lewis acid and any constituents of thepolymerization mixture may depend on various factors such as the typeand amount of the catalyst used to prepare the reactive polymer, thetype and amount of the Lewis acid, as well as the temperature at whichthe Lewis acid is introduced. In one or more embodiments, the Lewis acidand the reactive polymer are aged for at least 1 minute, in otherembodiments at least 5 minutes, in other embodiments at least 20minutes, in other embodiments at least 1 hour, and in other embodimentsat least 2 hours prior to any quenching of the polymerization system.

In one or more embodiments, the Lewis acid may be introduced to thepolymerization mixture at a location (e.g., within a vessel) where thepolymerization has been conducted. In other embodiments, the Lewis acidmay be introduced to the polymerization mixture at a location that isdistinct from where the polymerization has taken place. For example, theLewis acid may be introduced to the polymerization mixture in downstreamvessels including downstream reactors or tanks, in-line reactors ormixers, extruders, or devolatilizers.

In one or more embodiments, the amount of Lewis acid introduced to thepolymerization system may be defined relative to the amount oflanthanide metal within the catalyst system used to prepare the polymer(e.g., atoms of neodymium). In one or more embodiments, the molar ratioof Lewis acid to lanthanide metal in the lanthanide-containing compound(LA/Ln) is at least 0.5:1, in other embodiments at least 1:1, and inother embodiments at least 5:1. In these or other embodiments, the molarratio of Lewis acid to lanthanide metal (LA/Ln) is at most 150:1, inother embodiments at most 100:1, and in other embodiments at most 50:1.In one or more embodiments, the molar ratio LA/Ln is from about 0.5:1 toabout 150:1, in other embodiments from about 1:1 to about 100:1, and inother embodiments from about 5:1 to about 50:1.

Lewis Acids

As the skilled person appreciates, Lewis acids includes those compoundsthat react with a Lewis base to form a Lewis adduct. According to themechanism, the Lewis base donates a pair of electrons to the Lewis acid,which in turn accepts the electron pair. In one or more embodiments, theLewis acid is not a Bronsted-Lowry acid, and will not have an acidichydrogen atom.

In one or more embodiments, the Lewis acid may be selected from titaniumtetraalkoxides, boron trihalides, trihydrocarbyl boranes,trihydrocarbyloxy borates, trihydrocarbylsilyl halides,trihydrocarbylsilyl triflates, silicon tetrahalides, titaniumtetrahalides, aluminum trihalides, zinc dihalides, and phosphorustrihalides.

In one or more embodiments, the Lewis acid may be selected from borontrihalides, trihydrocarbyl boranes, trihydrocarbyloxy borates,trihydrocarbylsilyl halides, silicon tetrahalides, titaniumtetrahalides, and phosphorus trihalides.

In one or more embodiments, the Lewis acid may be selected from borontrihalides, trihydrocarbyloxy borates, titanium tetrahalides, phosphorustrihalides.

In one or more embodiments, a boron trihalide may be defined by theformula

where each X is individually a halogen atom. Suitable halogen atomsinclude fluoride, chloride, and bromide. In one or more embodiments,each X may be identical. For example, when each X is a fluoride atom,the boron trihalides may be a boron trifluoride.

In one or more embodiments, a trihydrocarbyloxy borate may be defined bythe formula

where each R is individually a monovalent organic group.

In one or more embodiments, the monovalent organic groups may includehydrocarbyl groups, which include, but are not limited to, alkyl,cycloalkyl, alkenyl, cycloalkenyl, aryl, allyl, aralkyl, alkaryl, oralkynyl groups. Hydrocarbyl groups also include substituted hydrocarbylgroups, which refer to hydrocarbyl groups in which one or more hydrogenatoms have been replaced by a substituent such as a hydrocarbyl,hydrocarbyloxy, silyl, or silyloxy group. In one or more embodiments,these groups may include from one, or the appropriate minimum number ofcarbon atoms to form the group, to about 20 carbon atoms. These groupsmay also contain heteroatoms such as, but not limited to, nitrogen,boron, oxygen, silicon, sulfur, tin, and phosphorus atoms.

In one or more embodiments, a titanium tetrahalide may be defined by theformula

where each X is individually a halogen atom. Suitable halogen atomsinclude fluoride, chloride, and bromide. In one or more embodiments,each X may be identical.

In one or more embodiments, a phosphorus trihalide may be defined by theformula

where each X is individually a halogen atom. Suitable halogen atomsinclude fluoride, chloride, and bromide. In one or more embodiments,each X may be identical.

In one or more embodiments, the Lewis acid may be part of a Lewisacid-Lewis base complex. For example, the Lewis acid boron trihalide maybe used as a boron trifluoride complex. Suitable Lewis bases for formingcomplexes include, but are not limited to, alcohols, water, mineralacids containing oxygen, water, aldehydes, amines, esters, thioesters,ethers, thioethers, ketones and nitriles.

In one or more embodiments, a ketone may be defined by the formula RCOR,where each R is independently a monovalent organic group. Representativeexamples of ketones suitable for use in boron trifluoride complexesinclude acetone, methyl ethyl ketone, dibutyl ketone, methyl isobutylketone, ethyl octyl ketone, 2,4-pentanedione, butyl cycloheptanone,acetophenone, amylphenyl ketone, butylphenyl ketone, benzophenone,phenyltolyl ketone, and quinone. Representative examples of borontrifluoride ketones complexes include boron trifluoride acetophenone andboron trifluoride benzophenone.

In one or more embodiments, an aldehyde may be defined by the formulaRCHO, where each R is independently a monovalent organic group.Representative examples of aldehydes suitable for use in borontrifluoride complexes include butyraldehyde, anisaldehyde, cinnamicaldehyde, isobutyraldehyde, heptaldehyde, dodecylaldehyde, benzaldehyde,phenylacetaldehyde, o-tolualdehyde, m-tolualdehyde, p-tolualdehyde,m-nitrobenzaldehyde, p-nitrobenzaldehyde, and m-hydrobenzaldehyde.Representative examples of boron trifluoride aldehyde complexes includeare boron trifluoride benzaldehyde and boron trifluoride tolualdehyde.

In one or more embodiments, an ester may be defined by the formulaR—COOR where each R is independently a monovalent organic group.Representative examples of esters include ethyl butyrate, ethyloctanoate, isopropyl hexanoate, amyl acetate, hexyl propionate, cetylacetate, ethyl benzoate, amyl benzoate, phenyl acetate, phenyl butyrate,and phenyl benzoate. Representative examples of boron trifluoride esterscomplexes include boron trifluoride ethyl benzoate, boron trifluorideethyl acetate and boron trifluoride phenyl acetate. One skilled in theart would readily be able to prepare thioester analogs based upon thedescription of esters provided.

In one or more embodiments, an ether may be defined by the formulaR—O—R, where each R is independently a monovalent organic group.Representative examples of ethers include ethoxybutane, butoxybutane,ethoxyoctane, isopropoxyhexane, propoxyhexane, ethoxybenzene, andamyloxybenzene. Representative examples of boron trifluoride ethercomplexes include boron trifluoride methyl t-butyl ether, borontrifluoride dibutyl ether, and boron trifluoride dimethyl ether. Oneskilled in the art would readily be able to prepare thioether analogsbased upon the description of ethers provided.

In one or more embodiments, a nitrile may be represented by the formulaRCN, where R is a monovalent organic group. Representative examples ofnitriles include acetonitrile, butyronitrile, acrylonitrile,benzonitrile, o-tolunitrile, m-tolunitrile, p-tolunitrile, andphenylacetonitrile. Representative examples of boron trifluoride nitrilecomplexes include boron trifluoride benzonitrile.

Quenching

In one or more embodiments, after the reaction between the reactivepolymer and the Lewis acid has been accomplished or completed, aquenching agent can be added to the polymerization mixture in order toprotonate the reaction product between the reactive polymer and theLewis acid, inactivate any residual reactive polymer chains, and/orinactivate the catalyst or catalyst components. The quenching agent mayinclude a protic compound, which includes, but is not limited to, analcohol, a carboxylic acid, an inorganic acid, water, or a mixturethereof. In particular embodiments, quenching with an alcohol, such asisopropanol, is employed since it has been observed that the use ofisopropyl alcohol contributes to certain desirable properties in thefinal polymer, such as desirable cold flow. An antioxidant such as2,6-di-tert-butyl-4-methylphenol may be added along with, before, orafter the addition of the quenching agent. The amount of the antioxidantemployed may be in the range of 0.2% to 1% by weight of the polymerproduct. Additionally, the polymer product can be oil extended by addingan oil to the polymer, which may be in the form of a polymer cement orpolymer dissolved or suspended in monomer. Practice of the presentinvention does not limit the amount of oil that may be added, andtherefore conventional amounts may be added (e.g., 5-50 phr). Usefuloils or extenders that may be employed include, but are not limited to,aromatic oils, paraffinic oils, naphthenic oils, vegetable oils otherthan castor oils, low PCA oils including MES, TDAE, and SRAE, and heavynaphthenic oils.

Polymer Recovery

Once the polymerization mixture has been quenched, the variousconstituents of the polymerization mixture may be recovered. In one ormore embodiments, the unreacted monomer can be recovered from thepolymerization mixture. For example, the monomer can be distilled fromthe polymerization mixture by using techniques known in the art. In oneor more embodiments, a devolatilizer may be employed to remove themonomer from the polymerization mixture. Once the monomer has beenremoved from the polymerization mixture, the monomer may be purified,stored, and/or recycled back to the polymerization process.

The polymer product may be recovered from the polymerization mixture byusing techniques known in the art. In one or more embodiments,desolventization and drying techniques may be used. For instance, thepolymer can be recovered by passing the polymerization mixture through aheated screw apparatus, such as a desolventizing extruder, in which thevolatile substances are removed by evaporation at appropriatetemperatures (e.g., about 100° C. to about 170° C.) and underatmospheric or sub-atmospheric pressure. This treatment serves to removeunreacted monomer as well as any low-boiling solvent. Alternatively, thepolymer can also be recovered by subjecting the polymerization mixtureto steam desolventization, followed by drying the resulting polymercrumbs in a hot air tunnel. The polymer can also be recovered bydirectly drying the polymerization mixture on a drum dryer.

Polymer Properties

In one or more embodiments, the polymers of this invention may becis-1,4-polydienes having a cis-1,4-linkage content that is greater than60%, in other embodiments greater than 75%, in other embodiments greaterthan 90%, in other embodiments greater than 95%, in other embodimentsgreater than 96%, in other embodiments greater than 97%, in otherembodiments greater than 98%, and in other embodiments greater than 99%,where the percentages are based upon the number of diene mer unitsadopting the cis-1,4 linkage versus the total number of diene mer units.Also, these polymers may have a 1,2-linkage content that is less than7%, in other embodiments less than 5%, in other embodiments less than2%, and in other embodiments less than 1%, where the percentages arebased upon the number of diene mer units adopting the 1,2-linkage versusthe total number of diene mer units. The balance of the diene mer unitsmay adopt the trans-1,4-linkage. The cis-1,4-, 1,2-, andtrans-1,4-linkage contents can be determined by infrared spectroscopy.

In one or more embodiments, the number average molecular weight (M_(n))of the cis-1,4-polydienes of this invention may be from about 1,000 toabout 1,000,000, in other embodiments from about 5,000 to about 200,000,in other embodiments from about 25,000 to about 150,000, and in otherembodiments from about 50,000 to about 120,000, as determined by usinggel permeation chromatography (GPC) calibrated with polystyrenestandards and Mark-Houwink constants for the polymer in question. Themolecular weight distribution or polydispersity (M_(w)/M_(n)) of thecis-1,4-polydienes of this invention may be from about 1.5 to about 5.0,and in other embodiments from about 2.0 to about 4.0. In these or otherembodiments, the cis-1,4-polydienes of this invention may have aM_(w)/M_(n) of less than 3.0, in other embodiments less than 2.5, inother embodiments less than 2.3, in other embodiments less than 2.2, inother embodiments less than 2.1, and in other embodiments less than 2.0.

In one or more embodiments, the cold-flow resistance of the polymer maybe measured by using a Scott plasticity tester. The cold-flow resistancemay be measured by placing a weight on a cylindrical button preparedfrom a sample of polymer. A button of the polymer sample may be preparedby molding approximately 2.5 g of the polymer, at 100° C. for 20 minutesto prepare a cylindrical button with a diameter of 15 mm and a height of12 mm. The button may be removed from the mold after it has cooled toroom temperature. The test may then be performed by placing the buttonin the Scott plasticity tester at room temperature and applying a 5-kgload to the sample. After 8 minutes, the residual sample gauge (i.e.,sample thickness) may be measured. Generally, the residual sample gaugecan be taken as an indication of the cold-flow resistance of thepolymer, with a higher residual sample gauge indicating better cold-flowresistance.

The polymer product produced by one or more embodiments of the presentinvention may be characterized by an advantageous cold flow resistance.This advantageous cold flow resistance may be represented as at least a10% increase, in other embodiments at least a 20% increase, in otherembodiments at least a 30% increase, in other embodiments at least a 40%increase, in other embodiments at least a 80% increase, and in otherembodiments at least a 100% increase, and in other embodiments at leasta 200% increase, and in other embodiments at least a 300% increase ingravitational cold flow as compared to similar polymeric compositions(i.e. cis-1,4-polydienes) that have not been treated with a Lewis acidaccording to aspects of this invention, where the accelerated cold flowresistance is determined using the Scott tester and analysis describedabove.

INDUSTRIAL APPLICATION

Advantageously, the cis-1,4-polydiene polymers of this invention areparticularly useful in preparing rubber compositions that can be used tomanufacture tire components. Rubber compounding techniques and theadditives employed therein are generally disclosed in The Compoundingand Vulcanization of Rubber, in Rubber Technology (2^(nd) Ed. 1973).

The rubber compositions can be prepared by using the polymers alone ortogether with other elastomers (i.e., polymers that can be vulcanized toform compositions possessing rubbery or elastomeric properties). Otherelastomers that may be used include natural and synthetic rubbers. Thesynthetic rubbers typically derive from the polymerization of conjugateddiene monomer, the copolymerization of conjugated diene monomer withother monomer such as vinyl-substituted aromatic monomer, or thecopolymerization of ethylene with one or more α-olefins and optionallyone or more diene monomers.

Exemplary elastomers include natural rubber, synthetic polyisoprene,polybutadiene, polyisobutylene-co-isoprene, neoprene,poly(ethylene-co-propylene), poly(styrene-co-butadiene),poly(styrene-co-isoprene), poly(styrene-co-isoprene-co-butadiene),poly(isoprene-co-butadiene), poly(ethylene-co-propylene-co-diene),polysulfide rubber, acrylic rubber, urethane rubber, silicone rubber,epichlorohydrin rubber, and mixtures thereof. These elastomers can havea myriad of macromolecular structures including linear, branched, andstar-shaped structures.

The rubber compositions may include fillers such as inorganic andorganic fillers. Examples of organic fillers include carbon black andstarch. Examples of inorganic fillers include silica, aluminumhydroxide, magnesium hydroxide, mica, talc (hydrated magnesiumsilicate), and clays (hydrated aluminum silicates). Carbon blacks andsilicas are the most common fillers used in manufacturing tires. Incertain embodiments, a mixture of different fillers may beadvantageously employed.

In one or more embodiments, carbon blacks include furnace blacks,channel blacks, and lamp blacks. More specific examples of carbon blacksinclude super abrasion furnace blacks, intermediate super abrasionfurnace blacks, high abrasion furnace blacks, fast extrusion furnaceblacks, fine furnace blacks, semi-reinforcing furnace blacks, mediumprocessing channel blacks, hard processing channel blacks, conductingchannel blacks, and acetylene blacks.

In particular embodiments, the carbon blacks may have a surface area(EMSA) of at least 20 m²/g and in other embodiments at least 35 m²/g;surface area values can be determined by ASTM D-1765 using thecetyltrimethylammonium bromide (CTAB) technique. The carbon blacks maybe in a pelletized form or an unpelletized flocculent form. Thepreferred form of carbon black may depend upon the type of mixingequipment used to mix the rubber compound.

The amount of carbon black employed in the rubber compositions can be upto about 50 parts by weight per 100 parts by weight of rubber (phr),with about 5 to about 40 phr being typical.

Some commercially available silicas which may be used include Hi-Sil™215, Hi-Sil™ 233, and Hi-Sil™ 190 (PPG Industries, Inc.; Pittsburgh,Pa.). Other suppliers of commercially available silica include GraceDavison (Baltimore, Md.), Degussa Corp. (Parsippany, N.J.), RhodiaSilica Systems (Cranbury, N.J.), and J. M. Huber Corp. (Edison, N.J.).

In one or more embodiments, silicas may be characterized by theirsurface areas, which give a measure of their reinforcing character. TheBrunauer, Emmet and Teller (“BET”) method (described in J. Am. Chem.Soc., vol. 60, p. 309 et seq.) is a recognized method for determiningthe surface area. The BET surface area of silica is generally less than450 m²/g. Useful ranges of surface area include from about 32 to about400 m²/g, about 100 to about 250 m²/g, and about 150 to about 220 m²/g.

The pH's of the silicas are generally from about 5 to about 7 orslightly over 7, or in other embodiments from about 5.5 to about 6.8.

In one or more embodiments, where silica is employed as a filler (aloneor in combination with other fillers), a coupling agent and/or ashielding agent may be added to the rubber compositions during mixing inorder to enhance the interaction of silica with the elastomers. Usefulcoupling agents and shielding agents are disclosed in U.S. Pat. Nos.3,842,111, 3,873,489, 3,978,103, 3,997,581, 4,002,594, 5,580,919,5,583,245, 5,663,396, 5,674,932, 5,684,171, 5,684,172 5,696,197,6,608,145, 6,667,362, 6,579,949, 6,590,017, 6,525,118, 6,342,552, and6,683,135, which are incorporated herein by reference.

The amount of silica employed in the rubber compositions can be fromabout 1 to about 100 phr or in other embodiments from about 5 to about80 phr. The useful upper range is limited by the high viscosity impartedby silicas. When silica is used together with carbon black, the amountof silica can be decreased to as low as about 1 phr; as the amount ofsilica is decreased, lesser amounts of coupling agents and shieldingagents can be employed. Generally, the amounts of coupling agents andshielding agents range from about 4% to about 20% based on the weight ofsilica used.

A multitude of rubber curing agents (also called vulcanizing agents) maybe employed, including sulfur or peroxide-based curing systems. Curingagents are described in Kirk-Othmer, ENCYCLOPEDIA OF CHEMICALTECHNOLOGY, Vol. 20, pgs. 365-468, (3^(rd) Ed. 1982), particularlyVulcanization Agents and Auxiliary Materials, pgs. 390-402, and A. Y.Coran, Vulcanization, ENCYCLOPEDIA OF POLYMER SCIENCE AND ENGINEERING,(2^(nd) Ed. 1989), which are incorporated herein by reference.Vulcanizing agents may be used alone or in combination.

Other ingredients that are typically employed in rubber compounding mayalso be added to the rubber compositions. These include accelerators,accelerator activators, oils, plasticizer, waxes, scorch inhibitingagents, processing aids, zinc oxide, tackifying resins, reinforcingresins, fatty acids such as stearic acid, peptizers, and antidegradantssuch as antioxidants and antiozonants. In particular embodiments, theoils that are employed include those conventionally used as extenderoils, which are described above.

All ingredients of the rubber compositions can be mixed with standardmixing equipment such as Banbury or Brabender mixers, extruders,kneaders, and two-rolled mills. In one or more embodiments, theingredients are mixed in two or more stages. In the first stage (oftenreferred to as the masterbatch mixing stage), a so-called masterbatch,which typically includes the rubber component and filler, is prepared.To prevent premature vulcanization (also known as scorch), themasterbatch may exclude vulcanizing agents. The masterbatch may be mixedat a starting temperature of from about 25° C. to about 125° C. with adischarge temperature of about 135° C. to about 180° C. Once themasterbatch is prepared, the vulcanizing agents may be introduced andmixed into the masterbatch in a final mixing stage, which is typicallyconducted at relatively low temperatures so as to reduce the chances ofpremature vulcanization. Optionally, additional mixing stages, sometimescalled remills, can be employed between the masterbatch mixing stage andthe final mixing stage. One or more remill stages are often employedwhere the rubber composition includes silica as the filler. Variousingredients including the polymers of this invention can be added duringthese remills.

The mixing procedures and conditions particularly applicable tosilica-filled tire formulations are described in U.S. Pat. Nos.5,227,425, 5,719,207, and 5,717,022, as well as European Patent No.890,606, all of which are incorporated herein by reference. In oneembodiment, the initial masterbatch is prepared by including the polymerof this invention and silica in the substantial absence of couplingagents and shielding agents.

The rubber compositions prepared from the polymers of this invention areparticularly useful for forming tire components such as treads,subtreads, sidewalls, body ply skims, bead filler, and the like.Preferably, the polymers of this invention are employed in tread andsidewall formulations. In one or more embodiments, these tread orsidewall formulations may include from about 10% to about 100% byweight, in other embodiments from about 35% to about 90% by weight, andin other embodiments from about 50% to about 80% by weight of thepolymer based on the total weight of the rubber within the formulation.

Where the rubber compositions are employed in the manufacture of tires,these compositions can be processed into tire components according toordinary tire manufacturing techniques including standard rubbershaping, molding and curing techniques. Typically, vulcanization iseffected by heating the vulcanizable composition in a mold; e.g., it maybe heated to about 140° C. to about 180° C. Cured or crosslinked rubbercompositions may be referred to as vulcanizates, which generally containthree-dimensional polymeric networks that are thermoset. The otheringredients, such as fillers and processing aids, may be evenlydispersed throughout the crosslinked network. Pneumatic tires can bemade as discussed in U.S. Pat. Nos. 5,866,171, 5,876,527, 5,931,211, and5,971,046, which are incorporated herein by reference.

In order to demonstrate the practice of the present invention, thefollowing examples have been prepared and tested. The examples shouldnot, however, be viewed as limiting the scope of the invention. Theclaims will serve to define the invention.

EXAMPLES

In the following examples, the Mooney viscosities (ML₁₊₄) of the polymersamples were determined at 100° C. by using a Monsanto Mooney viscometerwith a large rotor, a one-minute warm-up time, and a four-minute runningtime. The number average (M_(n)) and weight average (M_(w)) molecularweights of the polymer samples were determined by gel permeationchromatography (GPC). The GPC instrument was equipped with adifferential refractive index (RI) detector and an ultraviolet (UV)absorption detector. The cis-1,4-linkage, trans-1,4-linkage, and1,2-linkage contents of the polymer samples were determined by infraredspectroscopy.

The cold-flow resistance of the polymer was measured using a Scottplasticity tester, as described above.

Example 1 Synthesis of Unmodified cis-1,4-Polybutadiene

A nitrogen purged sealed glass vessel was charged with 92.9 g ofanhydrous hexanes and 240.4 g of a 20.8 wt. % solution of butadiene inhexanes. To this mixture was added sequentially 2.81 mL of a 1.03 Mtriisobutyl aluminum solution in hexanes, 0.91 mL of a 0.093 M neodymiumversatate solution in cyclohexanes, and 0.76 mL of a 0.167 Methylaluminum dichloride solution in hexanes. The polymerization mixturewas immediately placed in an agitating bath at 80° C. After 50 minutesof agitation, the polymerization was terminated by charging thepolymerization mixture with 3.0 ml of a 10 wt. % solution of2,6-di-tert-butyl-4-methylphenol in isopropanol. The polymer wascoagulated in 8 L of isopropanol containing 15 g of2,6-di-tert-butyl-4-methylphenol and then drum-dried. For polymercharacterization data, see Table 1.

Example 2 Synthesis of BF₃.Bu₂O Modified cis-1,4-Polybutadiene

A nitrogen purged sealed glass vessel was charged with 92.9 g ofanhydrous hexanes and 240.4 g of a 20.8 wt. % solution of butadiene inhexanes. To this mixture was added sequentially 2.81 mL of a 1.03 Mtriisobutylaluminum solution in hexanes, 0.91 mL of a 0.093 M neodymiumversatate solution in cyclohexanes, and 0.76 mL of a 0.167 Methylaluminum dichloride solution in hexanes. The polymerization mixturewas immediately placed in an agitating bath at 80° C. After 50 minutesof agitation, the polymerization was treated with a Lewis acid bycharging 1.70 mL of a 1.00 M BF₃.Bu₂O solution in hexanes and allowingthe polymerization solution to agitate at 50° C. After 30 minutes ofagitation, the polymerization was terminated by charging thepolymerization mixture with 3.0 ml of a 10 wt. % solution of2,6-di-tert-butyl-4-methylphenol in isopropanol. The polymer wascoagulated in 8 L of isopropanol containing 15 g of2,6-di-tert-butyl-4-methylphenol and then drum-dried. For polymercharacterization data, see Table 1.

Example 3 Synthesis of Unmodified cis-1,4-Polybutadiene

A nitrogen purged sealed glass vessel was charged with 92.9 g ofanhydrous hexanes and 240.4 g of a 20.8 wt. % solution of butadiene inhexanes. A preformed catalyst was prepared by mixing 6.31 mL of a 3.17 Mmethylaluminoxane solution in toluene, 1.53 mL of a 21.4 wt %1,3-butadiene in hexane solution, 2.16 mL of a 0.093 M neodymiumversatate solution in cyclohexane, 3.89 mL of a 1.09 Mdiisobutylaluminum hydride solution in hexane, and 0.80 mL of a 1.07 Mdiethylaluminum chloride solution in hexane. The catalyst was aged for15 minutes, diluted with 6.00 mL of toluene, and then 2.59 mL of thecatalyst solution was charged into the vessel containing butadiene andhexanes. The polymerization mixture was immediately placed in anagitating bath at 65° C. After 60 minutes of agitation, thepolymerization was terminated by charging the polymerization mixturewith 3.0 ml of a 10 wt. % solution of 2,6-di-tert-butyl-4-methylphenolin isopropanol. The polymer was coagulated in 8 L of isopropanolcontaining 15 g of 2,6-di-tert-butyl-4-methylphenol and then drum-dried.For polymer characterization data, see Table 1.

Example 4 Synthesis of BF₃.Bu₂O Modified cis-1,4-Polybutadiene

A nitrogen purged sealed glass vessel was charged with 92.9 g ofanhydrous hexanes and 240.4 g of a 20.8 wt. % solution of butadiene inhexanes. A preformed catalyst was prepared by mixing 6.31 mL of a 3.17 Mmethylaluminoxane solution in toluene, 1.53 mL of a 21.4 wt %1,3-butadiene in hexane solution, 2.16 mL of a 0.093 M neodymiumversatate solution in cyclohexane, 3.89 mL of a 1.09 Mdiisobutylaluminum hydride solution in hexane, and 0.80 mL of a 1.07 Mdiethylaluminum chloride solution in hexane. The catalyst was aged for15 minutes, diluted with 6.00 mL of toluene, and then 2.59 mL of thecatalyst solution was charged into the vessel containing butadiene andhexanes. The polymerization mixture was immediately placed in anagitating bath at 65° C. After 60 minutes of agitation, thepolymerization was treated with a Lewis acid by charging 2.00 mL of a1.00 M BF₃.Bu₂O (boron trifluoride dibutyl etherate) solution in hexanesand allowing the polymerization solution to agitate at 50° C. After 30minutes of agitation, the polymerization was terminated by charging thepolymerization mixture with 3.0 ml of a 10 wt. % solution of2,6-di-tert-butyl-4-methylphenol in isopropanol. The polymer wascoagulated in 8 L of isopropanol containing 15 g of2,6-di-tert-butyl-4-methylphenol and then drum-dried. For polymercharacterization data, see Table 1.

Table 1 summarizes the properties of the unmodified and BF₃.Bu₂Omodified cis-1,4-polydienes. Unmodified control samples made with twodifferent catalyst systems are shown in Examples 1 and 3. BF₃.Bu₂Omodified polymers made from the same two catalyst systems are shown inExamples 2 and 4.

The data in FIG. 1 indicates that, at the same polymer Mooney viscosity,the cis-1,4-polybutadiene samples modified with BF₃.Bu₂O (Example 2)show significantly higher residual sample gauge values and accordinglysignificantly better cold-flow resistance than the unmodified polymers.

The data in FIG. 2 indicates that, at the same polymer Mooney viscosity,the cis-1,4-polybutadiene samples modified with BF₃.Bu₂O (Example 4)show significantly higher residual sample gauge values and accordinglysignificantly better cold-flow resistance than the unmodified polymers.

TABLE 1 Comparison of Unmodified and BF₃•Bu₂O Modifiedcis-1,4-Polydienes Example 1 2 3 4 Catalyst System Formation In SituPreformed Nd per 100 gram Butadiene 0.17 0.05 (mmol) Bd Concentration(wt. %) 15 15 Polymerization Temperature (° C.) 80 65 PolymerizationTime (min) 50 60 BF₃•Bu₂O:Nd n/a 20 n/a 80 BF₃•Bu₂O Modification n/a 50n/a 50 Temperature (° C.) BF₃•Bu₂O Modification n/a 30 n/a 30 Time (min)% Conversion 99.8 99.8 >99 >99 ML₁₊₄ 40.6 49.1 29.5 40.3 t₈₀ 2.94 13.761.71 2.77 GPC (BR Universal Standard) M_(n) (×10³) (g/mol) 97.5 86.2114.7 118.4 M_(w) (×10³) (g/mol) 321.9 282.8 220.1 244.3 M_(w)/M_(n)3.30 3.28 1.92 2.06 % Cis 96.89 96.84 94.79 94.82 % Trans 2.20 2.24 4.564.52 % Vinyl 0.91 0.92 0.65 0.66 Cold Flow Gauge (mm @ 8 min) 2.38 3.651.76 2.40

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

What is claimed is:
 1. A method for preparing cis-1,4-polydienes having useful resistance to cold flow, the method comprising the steps of: (i) preparing a pre-formed catalyst by combining (a) a lanthanide-containing compound, (b) an alkylating agent, and (c) a halogen source; (ii) preparing a polymerization mixture by combining the pre-formed catalyst and conjugated diene monomer to thereby form a polymerization mixture that includes a reactive polymer; and (iii) adding a Lewis acid to the polymerization mixture including the reactive polymer, where said polymerization mixture undergoes a peak polymerization temperature, and where said step of adding a Lewis acid takes place after the peak polymerization temperature.
 2. The method of claim 1, where the lanthanide-based catalyst is aged for at least 1 hour.
 3. The method of claim 1, where the lanthanide-based catalyst is aged for at least 30 days.
 4. The method of claim 1, where the lanthanide-based catalyst comprises a lanthanide carboxylate, an aluminum hydride, and an organometallic halide.
 5. The method of claim 1, where the alkylating agent includes an aluminoxane and an organoaluminum compound represented by the formula AlR_(n)X_(3-n), where each R, which may be the same or different, is a monovalent organic group that is attached to the aluminum atom via a carbon atom, where each X, which may be the same or different, is a hydrogen atom, a halogen atom, a carboxylate group, an alkoxide group, or an aryloxide group, and where n is an integer of 1 to
 3. 6. The method of claim 1, where said step of polymerizing monomer takes place within a polymerization mixture including less than 20% by weight of organic solvent.
 7. The method of claim 1, where the Lewis acid is selected from the group consisting of titanium tetraalkoxides, boron trihalides, trihydrocarbyl boranes, trihydrocarbyloxy borates, trihydrocarbylsilyl halides, trihydrocarbylsilyl triflates, silicon tetrahalides, titanium tetrahalides, aluminum trihalides, zinc dihalides, and phosphorus trihalides.
 8. The method of claim 1, where the Lewis acid is selected from the group consisting of boron trihalides, trihydrocarbyl boranes, trihydrocarbyloxy borates, trihydrocarbylsilyl halides, silicon tetrahalides, titanium tetrahalides, and phosphorus trihalides.
 9. The method of claim 1, where the Lewis acid is selected from the group consisting of boron trihalides, trihydrocarbyloxy borates, titanium tetrahalides, phosphorus trihalides.
 10. The method of claim 1, where the Lewis acid is a boron trihalide defined by the formula

where each X is individually a halogen atom.
 11. The method of claim 1, where the Lewis acid is a trihydrocarbyloxy borate defined by the formula

where each R is individually a monovalent organic group.
 12. The method of claim 1, where the Lewis acid is a titanium tetrahalide defined by the formula

where each X is individually a halogen atom.
 13. The method of claim 1, where the Lewis acid is a phosphorus trihalide defined by the formula

where each X is individually a halogen atom.
 14. The method of claim 1, where the Lewis acid is part of a Lewis acid-Lewis base complex.
 15. The method of claim 1, where the method further comprises the step of adding a functionalizing agent to the polymerization system including a reactive polymer.
 16. The method of claim 1, where the method further comprises the step of adding a quenching agent to the polymerization system including a reactive polymer.
 17. A vulcanizable composition comprising: a filler, a curative and a cis-1,4-polydienes prepared by the method of claim 1, wherein the molecular weight distribution of the cis-1,4-polydienes is less than 2.06.
 18. A tire component prepared by employing the vulcanizable composition of claim
 17. 